Air diffuser



FIG. 1 is a front perspective view of an air diffuser showing my new design;

FIG. 2 is a perspective view of the ring thereof, shown separately for clarity of illustration;

FIG. 3 is a front perspective view thereof with the cover removed to show the air directing plate mounted thereon;

FIG. 4 is a front perspective view of the cover thereof, shown separately for clarity of illustration; and

FIG. 5 is a rear perspective view of FIG. 4. 

The ornamental design for an air diffuser, as shown and described. 